This invention relates to refractories such as are used in the steel industry. More particularly, this invention relates to reinforcement of refractories by the impregnation of the pores of refractories with fillers to increase the resistance of the refractories to heat fluctuation. The impregnated refractories are useful, for example, in the steel industry.
Refractories such as aluminas and alumina silicate, silicas, mullites, zirconias, alumina carbons, magnesias and dolomites have high resistance to changes in temperature. Therefore, they can be used as thermal insulators, especially when the temperature changes are large. For example, they are used in gate assemblies in the steel industry, to control the flow of molten steel on an assembly line. Refractory-lined components more readily withstand the intermittent changes in temperature encountered on the assembly line due to heating and cooling of steel carriers.
One problem encountered with using refractories is that repeated temperature changes result in structural cracking of the refractories. For example, in the steel industry refractories wear out from continual changes in temperatures. Therefore, the prior art has recognized the need for reinforcement of refractories. The prior art method for strengthening refractories involves impregnation of fillers into the refractories to seal their pores. With such impregnation, the refractory develops a higher and more uniform structural strength to withstand heat fluctuations.
Carbon bearing materials, including coal tar, tar pitch and carbon pitch have been used by prior art as fillers for refractories. To impregnate refractories, these carbon bearing materials must be heated in order to sufficiently decrease their viscosity to allow them to seep into the pores of the refractory.
One problem encountered in heating carbon bearing materials for use as fillers in refractories is that noxious fumes are created. These fumes must be eliminated from the air because they can be harmful to the health of factory personnel. They may also violate OSHA or EPA standards. The need for elimination of the noxious fumes increases the cost of producing refractories reinforced with carbon bearing materials.
Furthermore, the prior art refractories bleed and smoke in use when volatiles contained in the carbon bearing materials are not entirely removed during baking after the impregnation process.
The present invention overcomes the above-identified problems inherent in the prior art processes for making reinforced refractories and in the use of refractories made by such prior art processes.